How to make line height match font height?

Question

I've tried setting my line-height to 1em, however, there is still some space above and below the font (about 3px):

How can I set the line-height of my site to be exactly that of the font height?

JSFiddle: http://jsfiddle.net/uovjzrn6/1/

HTML:

Hello, world!

CSS:

body {
    font-size: 18px;
    line-height: 1em;
}

Answer 1

line-height: 0.75;

It saved may days.